The aircraft engine used in this discussion provides a typical example of a turbofan powerplant removal and installation procedures. The engine and all engine-mounted accessories form a QECA.
Access to the engine is provided by doors that can be raised and locked open. Directional references, such as right and left and clockwise and counterclockwise, apply to the engine as viewed from the aft or exhaust end of the engine.Removal and Replacement of an Auxiliary Power Unit (APU)
1. Open APU compartment access door latches and open door. Install door support rods. Open circuit breakers and switches as needed. [Figure 8-17]
2. Remove lower support shroud.
3. Disconnect APU harness, APU starter motor, and APU generator plugs from receptacles in upper shroud.
4. Disconnect APU generator control plug from receptacle in upper shroud.
5. Disconnect exhaust gas temperature (EGT) indicating system plug from receptacle in upper shroud.
6. Disconnect bleed load control air line from fitting in upper shroud.
7. Disconnect fuel hose from elbow on low pressure fuel filter. Collect dripping fuel in a suitable container.
8. Disconnect fire detection sensor element plug from receptacle in upper shroud.
9. Disconnect APU to upper shroud bonding jumper.
10. Remove clamp attaching bleed air duct coupling to turbine plenum bleed air flange.
11. Push bleed air duct coupling outboard as far as it will go.
12. Move compressor air inlet duct lock handle outboard until heel of cam is free from spring arm.
13. Rotate compressor plenum downward so that compressor air inlet opening in plenum no longer matches air inlet duct in upper shroud.
14. Install hoist assemblies to brackets in APU compartment with pins.
15. When using F80002 cradle, insert tubes in cradle base and secure in place with pins.
16. Attach hoist cables to cradle assembly tubes with pins.
17. Install cradle base on APU powerplant and secure in place with pins.
18. Pull hoist cables taut to remove load from APU engine mounts.
19. Remove nuts, washers, and bolt fastening mount caps to engine mount brackets. Do not remove cap and mount bracket hinge bolts. Open mount caps.
20. Lower powerplant slowly. Guide unit to clear bleed air duct coupling, fuel line, and airplane structure.
21. After the unit is set on transportation dolly, slacken hoist cables.
22. Disconnect hoist cables from tubes by removing pins.
Install APU Powerplant
1. Position APU powerplant, installed on a cradle base, directly under APU compartment.
2. Connect hoist cables to tubes with pins.
3. Rotate compressor plenum air inlet opening down. Slowly raise APU powerplant. Guide unit to clear airplane structure.
4. With the APU in place, make sure the seal of the cooling air inlet duct is touching the cooling fan flanges.
5. Close mount caps and install bolts, washers, and nuts. Tighten nuts to a torque range of 30 to 40 poundinches.
6. Rotate compressor plenum to match compressor air inlet opening in plenum with air inlet duct in upper shroud.
7. Move compressor air inlet duct lock handle inboard until heel of cam falls behind spring arm. Install locking screws and two nuts to secure locking handle.
8. Slacken hoist cables and disconnect cables from tubes by removing pins.
9. Remove pins securing cradle base to APU powerplant and remove cradle.
10. Remove pins securing hoist to brackets in APU compartment and remove hoists.
11. Slide bleed air duct coupling inboard as far as it will go.
12. Install clamp attaching bleed air duct coupling to turbine plenum bleed air flange. Tighten clampcoupling nut to a torque range of 45 to 55 pound-inches.
13. Connect fuel hose to elbow on low pressure fuel filter.
14. Connect fire detection sensor element plug to receptacle on upper shroud and safety wire.
15. Connect bleed load control air line to fitting in upper shroud.
16. Connect EGT indicating system plug to receptacle in upper shroud and safety wire.
17. Connect APU generator control plug to receptacle in upper shroud and safety wire.
18. Connect APU harness, APU starter motor, and APU generator plugs to receptacles in upper shroud and safety wire connectors.
19. Connect APU to upper shroud bonding jumper.
20. Depreserve, or purge, the fuel system by motoring.